LESIONAL ALOPECIA-AREATA T-LYMPHOCYTES DOWN-REGULATE EPITHELIAL-CELL PROLIFERATION

Alopecia areata is characterized by peribulbar infiltration by activat ed T cells, The function of these T cells in the pathogenesis is unkno wn. To elucidate the potential role of lesional T cells in the regulat ion of hair growth, T-cell clones from the margin of involved alopecia areata lesions from three patients were obtained by cloning, using th e limiting dilution method, Of these T-cell clones, 31 were CD4(+)CD8( -), 15 were CD8(+)CD4(-) and 2 were CD4(-)CD8(-). The T-cell clones we re activated and the supernatant harvested 24 h later and tested for i ts capacity to regulate proliferation of neonatal keratinocytes, The m ajority of the T-cell clone supernatants inhibited epithelial cell pro liferation in a dose-dependent fashion, When the cytokine profiles of conditioned T-cell medium were compared with the growth-regulatory cap acity, it tvas found that T-cell clones that released high amounts of interferon gamma and/or tumour necrosis factor alpha inhibited keratin ocyte growth, In conclusion, T cells derived from the margin of active alopecia areata lesions are able to downregulate epithelial cell prol iferation, This points to an important role of the immune system, espe cially the T cells, in this disease.